Chair base



FIG. 1 is a perspective view of a chair base according to the invention.

FIG. 2 is a top view of the chair base.

FIG. 3 is a front view of the chair base.

FIG. 4 is a back view of the chair base.

FIG. 5 is a first side view of the chair base; and,

FIG. 6 is a second side view of the chair base.

The broken lines shown in the drawing are for the purpose of illustrating environmental structure and form no part of the claimed design. 

CLAIM The ornamental design for a chair base, as shown and described herein. 